This invention relates generally to a means of rapidly and accurately counting large quantities of objects, and more specifically to counting dual-in-line plastic (DIP) integrated circuits (IC's), packaged, as is customary in the semiconductor industry, in extruded plastic cylinders sometimes called "rails".
An increasingly large fraction of the total product of the semiconductor industry consists of linear and digital integrated circuits. The volume of production and the aggregate economic value of these integrated circuits gives rise to a need for improved methods of counting in order to facilitate inventory control in their manufacture and distribution.
Many of the conventional counting methods are of limited usefulness in the case of IC's packaged in rails. Methods based on weight are handicapped by the substantial and uncertain weight of the rail itself. Labels or other markings on the rail itself, and the lack of an optically conspicuous line of demarkation between contiguous IC's, lead to difficulty in the case of optical counting methods. Magnetic methods are unduly sensitive to variations from type to type in the magnetic properties of IC's and, indeed, some IC's are virtually nonmagnetic.
Possible methods based on electrical capacity typically require that the IC being counted be well separated (singulated) from its neighbors. Also, capacity measuring techniques operating at lower carrier frequencies are adversely affected by the antistatic coating used on rails for IC's.